In same Young's Double slit experiment set up two sources of light produces fringes of width $0.2 \;mm$ and $0.3 \;mm$ The ratio of wave length of two light sources is

Question

$(a)\;\frac{2}{3} \\ (b)\;\frac{4}{9} \\ (c)\;\frac{1}{3} \\ (d)\frac{2}{1}$